diff options
Diffstat (limited to 'third_party/abseil_cpp/absl/synchronization/notification.h')
| -rw-r--r-- | third_party/abseil_cpp/absl/synchronization/notification.h | 123 |
1 files changed, 0 insertions, 123 deletions
diff --git a/third_party/abseil_cpp/absl/synchronization/notification.h b/third_party/abseil_cpp/absl/synchronization/notification.h deleted file mode 100644 index 9a354ca2c0..0000000000 --- a/third_party/abseil_cpp/absl/synchronization/notification.h +++ /dev/null @@ -1,123 +0,0 @@ -// Copyright 2017 The Abseil Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// https://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. -// -// ----------------------------------------------------------------------------- -// notification.h -// ----------------------------------------------------------------------------- -// -// This header file defines a `Notification` abstraction, which allows threads -// to receive notification of a single occurrence of a single event. -// -// The `Notification` object maintains a private boolean "notified" state that -// transitions to `true` at most once. The `Notification` class provides the -// following primary member functions: -// * `HasBeenNotified() `to query its state -// * `WaitForNotification*()` to have threads wait until the "notified" state -// is `true`. -// * `Notify()` to set the notification's "notified" state to `true` and -// notify all waiting threads that the event has occurred. -// This method may only be called once. -// -// Note that while `Notify()` may only be called once, it is perfectly valid to -// call any of the `WaitForNotification*()` methods multiple times, from -// multiple threads -- even after the notification's "notified" state has been -// set -- in which case those methods will immediately return. -// -// Note that the lifetime of a `Notification` requires careful consideration; -// it might not be safe to destroy a notification after calling `Notify()` since -// it is still legal for other threads to call `WaitForNotification*()` methods -// on the notification. However, observers responding to a "notified" state of -// `true` can safely delete the notification without interfering with the call -// to `Notify()` in the other thread. -// -// Memory ordering: For any threads X and Y, if X calls `Notify()`, then any -// action taken by X before it calls `Notify()` is visible to thread Y after: -// * Y returns from `WaitForNotification()`, or -// * Y receives a `true` return value from either `HasBeenNotified()` or -// `WaitForNotificationWithTimeout()`. - -#ifndef ABSL_SYNCHRONIZATION_NOTIFICATION_H_ -#define ABSL_SYNCHRONIZATION_NOTIFICATION_H_ - -#include <atomic> - -#include "absl/base/macros.h" -#include "absl/synchronization/mutex.h" -#include "absl/time/time.h" - -namespace absl { -ABSL_NAMESPACE_BEGIN - -// ----------------------------------------------------------------------------- -// Notification -// ----------------------------------------------------------------------------- -class Notification { - public: - // Initializes the "notified" state to unnotified. - Notification() : notified_yet_(false) {} - explicit Notification(bool prenotify) : notified_yet_(prenotify) {} - Notification(const Notification&) = delete; - Notification& operator=(const Notification&) = delete; - ~Notification(); - - // Notification::HasBeenNotified() - // - // Returns the value of the notification's internal "notified" state. - bool HasBeenNotified() const { - return HasBeenNotifiedInternal(&this->notified_yet_); - } - - // Notification::WaitForNotification() - // - // Blocks the calling thread until the notification's "notified" state is - // `true`. Note that if `Notify()` has been previously called on this - // notification, this function will immediately return. - void WaitForNotification() const; - - // Notification::WaitForNotificationWithTimeout() - // - // Blocks until either the notification's "notified" state is `true` (which - // may occur immediately) or the timeout has elapsed, returning the value of - // its "notified" state in either case. - bool WaitForNotificationWithTimeout(absl::Duration timeout) const; - - // Notification::WaitForNotificationWithDeadline() - // - // Blocks until either the notification's "notified" state is `true` (which - // may occur immediately) or the deadline has expired, returning the value of - // its "notified" state in either case. - bool WaitForNotificationWithDeadline(absl::Time deadline) const; - - // Notification::Notify() - // - // Sets the "notified" state of this notification to `true` and wakes waiting - // threads. Note: do not call `Notify()` multiple times on the same - // `Notification`; calling `Notify()` more than once on the same notification - // results in undefined behavior. - void Notify(); - - private: - static inline bool HasBeenNotifiedInternal( - const std::atomic<bool>* notified_yet) { - return notified_yet->load(std::memory_order_acquire); - } - - mutable Mutex mutex_; - std::atomic<bool> notified_yet_; // written under mutex_ -}; - -ABSL_NAMESPACE_END -} // namespace absl - -#endif // ABSL_SYNCHRONIZATION_NOTIFICATION_H_ |